What Privilege Law Applies to State Law Claims Within a Federal Court’s Supplemental Jurisdiction?

January 4, 2001

Federal common law generally applies to attorney-client privilege issues arising in federal question cases, while state privilege law generally applies in diversity cases. What law applies to state law claims within a federal court’s supplemental jurisdiction?

Not many courts have addressed this issue, but Simon Property Group v. mySimon, Inc., 194 F.R.D. 644, 646 (S.D. Ind. 2000) indicated that “where the principal claims in a lawsuit arise under federal law, the presence of some state law claims within the court’s supplemental jurisdiction generally should not affect the court’s obligation to apply federal law.”

Although this issue may not commonly arise, lawyers should always know what law will apply to each privilege issue, because the privilege law can differ dramatically from jurisdiction to jurisdiction.